Volume 9, Issue 4 (April 2012)
Characterization of the Master Curve Based Fracture Toughness of ORNL TSE5 Steel and Unirradiated and Irradiated ASTM A203D 3.5 % Ni Steel by the IGCAR Procedure
The Indira Gandhi Centre for Atomic Research (IGCAR) procedure for predicting the master curve (MC) reference temperature T0 has been further validated via its application to ORNL thermal shock experiment (TSE) 5 steel, an A508 Cl.2 steel that has been widely characterized in the literature. The procedure also was applied to ASTM A203D 3.5% Ni steel tested at IGCAR in virgin and irradiated states. The IGCAR procedure involves the application of the inverse Wallin strain rate equation to TQSchdy, the dynamic reference temperature obtained from Charpy tests using the modified Schindler procedure corresponding to a stress intensity factor rate of ∼106 MPa√m.s−1. A direct correlation of TQSchdy to T0 is also used. The larger of the estimates from these two, namely, TQSchW, provides an accurate and acceptably conservative estimate of the reference temperature TQ-est for steels with TQSchdy ≤ 60°C; for steels with TQSchdy>60°C, TQ-est=the larger of TQSchW and TQM2. The value of TQ-est obtained via the IGCAR procedure is termed TQ-IGC. Mostly, TQM2 gives the most conservative estimate, and TQBT (based on the value of TD obtained from instrumented Charpy V-notch impact tests) has a tendency toward accuracy, provided a robust estimate of TD can be obtained (which is not always the case). The IGCAR procedure was compared with two other conservative lower-bound (LB) procedures (Schindler-LB and Merkle-LB procedures), and it was shown that the IGCAR procedure with a 1% MC provides an LB curve without the difficulties involved in using the more tortuous calculations necessary for applying the Schindler- and Merkle-LB procedures. For the irradiated A203D steel, the shift in the estimated T0 was ΔTQ-IGC=340°C.